Found it!

Memento mori

Steve Bell gets it right, as usual. I wanted to post this next to Tom Raworth's wonderful take on the Hirst skull, but I can't find it anywhere. Perhaps someone can help. (Tom?) It's going to be the season of the crystal skull, I imagine, with the fourth Indiana Jones film and the news that all the crystal skulls in the hands of the world's museums were actually sculpted out of caked snot by a German cheese-maker in the late nineteenth century, or something to that effect. Ho ho.